CV joint, they do wear with age so the ball bearings move around in the cage, refurb one just have a bigger ball bearing to take up the slack.
The drive shafts i looked at are 328 so froma medium case diff, you may have to swap over the dust cap.
jason
BMW e21 race car supercharged s14 cage and fabrication by www.chizfab.com
Z3M Coupe
2.8 Z3 Coupe
Caterham Supersport
Clio 172 Cup factory race car(50%)
Ferrari 348 Challenge track car
I've already been chatting to someone about an M20 switch but the M52 lump has more astetic appeal although no way would i be doing the work as i've read the threads and don't have the time or patience.....
I would also look at a tuned M10 engine as i'm not looking for massive power gains as its the interior and exterior i'm concenstrating on most of all, i would just prefer more pokey than 90horses or more like 40 at present even with the weber twin choke carb.